In the design and operation of stapling guns, it is desirable to be able to provide the gun with a selection of forces for driving the staples. Usually, the provision of a high and a low force is sufficient for most purposes. The high force is desirable when the staples are being driven into hard material and the low force is desirable for normal use, simply because it is much harder work to successfully compress the spring to the high force. It is desirable, then, to be able to use low force when it is possible. Various constructions have been used in the past to provide for this selection of driving forces, a stapler of this kind being shown in the U.S. patent of Johnson No. 3,275,212. These constructions of the past have been expensive and intricate and have not been adapted to construction by modern manufacturing methods. Furthermore, they have been difficult for a person of average strength to manipulate. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a stapler having a ready-operable means for changing the staple-driving force.
Another object of this invention is the provision of a stapler having a force-changing means which is simple in construction and which can be readily operated by a person of average strength.
A further object of the present invention is the provision of a dual-force stapler of rugged construction which is not easily rendered inoperative.
It is another object of the instant invention to provide a stapler which is capable of a long life of useful service with a minimum of maintenance.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.